Photoemission study of electronic structure of the half-metallic ferromagnet ${\text{Co}}_3{\text{Sn}}_2{\text{S}}_2$

Surface electronic structure of polycrystalline and single-crystalline samples of the half-metallic ferromagnet ${\text{Co}}_3{\text{Sn}}_2{\text{S}}_2$ was studied by means of angle-resolved and core-level photoemissions. The experiments were performed in temperature regimes both above and below a Curie temperature of 176.9 K. The spectroscopic results are compared to local-spin density approximation band-structure calculations for the bulk samples. It is found that the surface sensitive experimental data are generally reproduced by the bulk computation suggesting that the theoretically predicted half-metallic properties of ${\text{Co}}_3{\text{Sn}}_2{\text{S}}_2$ are retained at the surface.

Figure 1

(Color online) (a) Crystal structure of ${\text{Co}}_3{\text{Sn}}_2{\text{S}}_2$ with rhombohedral basis. Axes of the hexagonal basis are also indicated. [(b)–(d)] LEED images obtained from (111) surface at different primary electron-beam energies. Bars denote scaling of the reciprocal lattice with electron-beam energy. (e) Two possible surface terminations [(i) and (ii), see text] obtained in experiments.

Figure 2

Core-level PE spectra measured for polycrystalline and single-crystalline samples. Results of the least-squares fit analysis are shown by thin lines underneath the $\text{S}2p$ spectra.

Figure 3

(Color online) Electronic structure calculated for bulk ${\text{Co}}_3{\text{Sn}}_2{\text{S}}_2$ with (a) unpolarized and (b) polarized spins. (c) Brillouin zone of the compound. Rhombohedral axis intersects the border of the BZ at the L point while (111) axis crosses it at the T point. The surface projection of the BZ is constructed according to the hexagonal description of the unit cell.

Figure 4

Angle-integrated valence-band PE spectra of [(a) and (b)] polycrystalline and [(c) and (d)] single-crystalline samples [solid lines] compared with the calculated DOS convoluted with a Gaussian (150 meV, FWHM) (diamonds).

Figure 5

(Color online) Angle-resolved PE spectra taken at $h\nu =21.2\text{eV}$ along the (a) $\overline{\Gamma }\text{−}\overline{M}$ and (b) $\overline{\Gamma }\text{−}\overline{K}$ directions as well as at $h\nu =40.8\text{eV}$ along the $\overline{\Gamma }\text{−}\overline{M}$ (c) direction (${\mathbf{k}}_{\parallel }$-momentum vector parallel to the sample surface). (d) 3D color plot of PE intensity. Theoretical bands are shown by black (high BE) and white $\left(E_F\right)$ dots.

Figure 6

(Color online) Angle-resolved PE spectra taken at $h\nu =70\text{eV}$ along the $\overline{\Gamma }\text{−}\overline{M}$ direction with linear (top) horizontal and (bottom) vertical light polarizations. Theoretical bands are shown by black (high BE) and white $\left(E_F\right)$ dots.

Figure 7

(Color online) (a) 3D plot of angle-resolved PE intensity close to $E_F$ taken with $h\nu =21.2\text{eV}$ along the $\overline{\Gamma }\text{−}\overline{K}$ direction in the close vicinity of 40 K. (b) Momentum distribution curves measured at the Fermi energy above (solid dots) and below (open dots) the Curie temperature (see text).